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Android Introduction

Android Introduction. Hello World. Goal. Create a very simple application Run it on a real device Run it on the emulator Examine its structure. Google Tutorial. We will follow the tutorial at: http://developer.android.com/resources/tutorials/hello-world.html

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Android Introduction

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  1. Android Introduction Hello World @2011 Mihail L. Sichitiu

  2. Goal • Create a very simple application • Run it on a real device • Run it on the emulator • Examine its structure @2011 Mihail L. Sichitiu

  3. Google Tutorial • We will follow the tutorial at: http://developer.android.com/resources/tutorials/hello-world.html • Start Eclipse (Start -> All Programs -> Eclipse) • Create an Android Virtual Device (AVD) • Create a New Android Project @2011 Mihail L. Sichitiu

  4. Package Content All source code here Java code for our activity Generated Java code Helps link resources to Java code All non-code resources Layout of the activity Images Strings used in the program Android Manifest @2011 Mihail L. Sichitiu

  5. Android Manifest • <?xml version="1.0" encoding="utf-8"?> • <manifest xmlns:android="http://schemas.android.com/apk/res/android" • package="com.example.helloandroid" • android:versionCode="1" • android:versionName="1.0"> • <application android:icon="@drawable/icon" android:label="@string/app_name"> • <activity android:name=".HelloAndroid" • android:label="@string/app_name"> • <intent-filter> • <action android:name="android.intent.action.MAIN" /> • <category android:name="android.intent.category.LAUNCHER" /> • </intent-filter> • </activity> • </application> • </manifest> @2011 Mihail L. Sichitiu

  6. Activity • An Android activity is focused on a single thing a user can do. • Most applications have multiple activities @2011 Mihail L. Sichitiu

  7. Activities start each other @2011 Mihail L. Sichitiu

  8. Revised HelloAndroid.java Inherit from the Activity Class package com.example.helloandroid;import android.app.Activity;import android.os.Bundle;import android.widget.TextView;public class HelloAndroid extends Activity {   /** Called when the activity is first created. */   @Override   public void onCreate(Bundle savedInstanceState) {       super.onCreate(savedInstanceState);TextView tv = new TextView(this);       tv.setText("Hello, Android – by hand");       setContentView(tv);   }} Set the view “by hand” – from the program @2011 Mihail L. Sichitiu

  9. Run it! @2011 Mihail L. Sichitiu

  10. /res/layout/main.xml <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/hello" /> </LinearLayout> Further redirection to /res/values/strings.xml @2011 Mihail L. Sichitiu

  11. /res/values/strings.xml <?xml version="1.0" encoding="utf-8"?> <resources> <string name="hello">Hello World, HelloAndroid – by resources!</string> <string name="app_name">Hello, Android</string> </resources> @2011 Mihail L. Sichitiu

  12. HelloAndroid.java package com.example.helloandroid; import android.app.Activity; import android.os.Bundle; public class HelloAndroid extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); } } Set the layout of the view as described in the main.xml layout @2011 Mihail L. Sichitiu

  13. /gen/R.java package com.example.helloandroid;public final class R {    public static final class attr {    }    public static final class drawable {        public static final int icon=0x7f020000;    }    public static final class id {        public static final int textview=0x7f050000;    }    public static final class layout {        public static final int main=0x7f030000;    }    public static final class string {        public static final int app_name=0x7f040001;        public static final int hello=0x7f040000;    }} @2011 Mihail L. Sichitiu

  14. Run it! @2011 Mihail L. Sichitiu

  15. Introduce a bug package com.example.helloandroid;import android.app.Activity;import android.os.Bundle;public class HelloAndroid extends Activity {    /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        Object o = null;        o.toString();        setContentView(R.layout.main);    }} @2011 Mihail L. Sichitiu

  16. Run it! @2011 Mihail L. Sichitiu

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